What's the difference? The difference is how they respond to their lighting rheostat being turned down.
- Glass becomes dim by mixing the RGB colors of the overlays toward black.
- Glass (tranlsucent) becomes dim by mixing the alpha channel of the overlays toward transparent.
- Use "glass" if you are using the layer as a "mask" to block elements behind it.
- Use "glass (translucent) if you are using the layer as an "overlay" to draw on top of other elements.